我想从类列表中生成类的数组列表。我教科书上的代码是这样的：
产品类别：
abstract class Product {
protected float price;
// return the price of a particular product
abstract float price();
}
class ComputerPart extends Product {
public ComputerPart(){
}
public ComputerPart(float p) {
price = p;
}
@Override
public float price() { return price; }
}
class Motherboard extends ComputerPart {
protected String manufacturer;
public Motherboard(){
}
public Motherboard(String mfg, float p) {
super(p);
manufacturer = mfg;
}
public String getManufacturer() { return manufacturer; }
}
class RAM extends ComputerPart {
protected int size;
protected String manufacturer;
public RAM(){
}
public RAM(String mfg, int size, float p) {
super(p);
this.manufacturer = mfg;
this.size = size;
}
public String getManufacturer() {
return manufacturer;
}
}
class Drive extends ComputerPart {
protected String type;
protected int speed;
public Drive(){
}
public Drive(String type, int speed, float p) {
super(p);
this.type = type;
this.speed = speed;
}
public String getType() { return type; }
public int getSpeed() { return speed; }
}
}
class Peripheral extends Product {
public Peripheral(){
}
public Peripheral(float p) {
price = p;
}
@Override
public float price() { return price; }
}
class Printer extends Peripheral {
protected String model;
public Printer(){
}
public Printer(String model, float p) {
super(p);
this.model = model;
}
public String getModel() { return model; }
}
class Monitor extends Peripheral {
protected String model;
public Monitor(String model, float p) {
super(p);
this.model = model;
}
public String getModel() { return model; }
}
class Service extends Product {
public Service(){
}
public Service(float p) {
price = p;
}
@Override
public float price() { return price; }
}
class AssemblyService extends Service {
String provider;
public AssemblyService(){
}
public AssemblyService(String pv, float p) {
super(p);
provider = pv;
}
public String getProvider() { return provider; }
}
class DeliveryService extends Service {
String courier;
public DeliveryService(){
}
public DeliveryService(String c, float p) {
super(p);
courier = c;
}
public String getCourier() { return courier; }
}
class Cheese extends Product {
public Cheese(){
}
public Cheese(float p) {
price = p;
}
@Override
public float price() { return price; }
}
class Cheddar extends Cheese {
public Cheddar(){
}
public Cheddar(float p) {
super(p);
}
}
class Mozzarella extends Cheese {
public Mozzarella(){
}
public Mozzarella(float p) {
super(p);
}
}
class Fruit extends Product {
public Fruit(){
}
public Fruit(float p) {
price = p;
}
@Override
public float price() { return price; }
}
class Apple extends Fruit {
public Apple(){
}
public Apple(float p) {
super(p);
}
}
class Orange extends Fruit {
public Orange(){
}
public Orange(float p) {
super(p);
}
}
computerorder类为：
public class ComputerOrder<T extends Product> extends GenericOrder<T> {
float price;
String ProductsSpecification;
String ProductsType;
private List<T> products;//the list of items
Random rand = new Random();
int number;
private Class[] types = {ComputerPart.class, Motherboard.class, RAM.class,
Drive.class, Peripheral.class, Printer.class, Monitor.class,
Service.class,
AssemblyService.class, DeliveryService.class,};
private String[] simpleName = {"ComputerPart", "Motherboard", "RAM",
"Drive", "Peripheral", "Printer", "Monitor", "Service",
"AssemblyService", "DeliveryService",};
public ComputerOrder() {
products = new ArrayList<>();
number = rand.nextInt(99999)+1;
}
public void addProduct(T t) {
if (t instanceof ComputerPart) {
products.add(t);
}
if (t instanceof Service) {
products.add(t);
}
if (t instanceof Peripheral) {
products.add(t);
}
}
@Override
public void print() {
System.out.println("Order Number: " + this.number);
for (int i = 0; i < products.size(); i++) {
System.out.println("Item " + (i+1) +" : " +
(products.get(i).getClass().getSimpleName()) +
" Price: " +products.get(i).price);
}
}
public int getNumberOfProducts() {
return products.size();
}
public List<T> getProducts() {
return products;
}
public void setProducts(List<T> products) {
this.products = products;
}
public float getPrice() {
return price;
}
public void setPrice(float price) {
this.price = price;
}
public String getProductsSpecification() {
return ProductsSpecification;
}
public void setProductsSpecification(String ProductsSpecification) {
this.ProductsSpecification = ProductsSpecification;
}
public String getProductsType() {
return ProductsType;
}
public void setProductsType(String ProductsType) {
this.ProductsType = ProductsType;
}
然后我创建了一个DataGenerator类，该类应生成随机的Product对象：
final private Class[] comptypes = {ComputerPart.class, Motherboard.class, RAM.class,
Drive.class, Peripheral.class, Printer.class, Monitor.class, Service.class,
AssemblyService.class, DeliveryService.class,};
Product computernext() {
try {
return (ComputerPart)
comptypes [rand.nextInt(comptypes.length)].newInstance();
}
catch (IllegalAccessException | InstantiationException e){
throw new RuntimeException(e);
}
}
Product computerDataGenerator() {
Product t = new genericstest.DataGenerator().computernext();
if (t instanceof RAM) {
((RAM) t).manufacturer = generateRAM();
((RAM) t).size = intDataGenerator();
((RAM) t).price = rand.nextFloat()*100;
}
if (t instanceof Motherboard) {
((Motherboard) t).manufacturer = generateMotherboard();
((Motherboard) t).price = rand.nextFloat()*100;
}
if (t instanceof Drive) {
((Drive) t).type = generateMotherboard();
((Drive) t).price = rand.nextFloat()*100;
}
return t;
}
public static void main（String [] args）{
DataGenerator gen = new DataGenerator();
for (int i = 0; i < 5; i++) {
System.out.println(gen.computernext());
}
}
但是当我实现它时，我得到了很多实例化异常。我查看了我的版本和教科书代码，没有看到任何差异，但是有人看到我错过的错误了吗？
答案 0 :(得分：0)
您没有为我们提供足够的代码来绝对确定问题，但是仅通过阅读您提供的内容，就会由于以下两个原因之一而引发实例化错误：
ComputerPart类不是Product的子类。comptypes中包含的一个类不是ComputerPart的子类。为确保comptypes中包含的每个类都是一个 product ，您应像这样对数组放置类型约束：
final private Class<Product>[] comptypes
这将确保该数组中的每个类都实现或扩展Product。
如果您可以为我们提供更多信息，那么我可以为您提供更好的答案。